At present, along with continuous growth of various communication services, an Optical Network Unit (ONU) is widely applied to optical fibre communications. Correspondingly, types of ONU control chips are gradually increased, and there may exist great differences even among different series of control chips of the same manufacturer. Each control chip corresponds to a software version during software setting, and if such a setting manner is adopted for the same product, big troubles may be brought to external field upgrading and use of users. For example: two sets and even more sets of software versions are required to be provided for the same product after two and even more control chips adopting different Advanced Risc Machine (ARM) kernels are used in sequence, which may cause low external field upgrading efficiency, more complicated upgrading method, inconvenience in use of a user and more difficulty in management.